This invention relates to a planing type boat and, more particularly, to a planing type runabout capable of being driven at high speeds by an engine such as an outboard motor.
There has been known a planing type boat which, for improving the stability of the boat, has a water ballast in a chamber provided at the bottom of the boat. There has also been known a boat of this type which, as shown in FIG. 1 illustrating the boat in a planing state, has a water ballast chamber a formed with a water outlet b in the aft portion thereof and an air inlet c in the forward portion thereof. According to this latter structure, as the boat starts planing, water in the water ballast chamber a is automatically discharged by a combined action of inertia, gravity and aspiration induced by the outside flow of water whereby the weight of the boat is reduced and its buoyancy is increased resulting in improvement in the running performances of the boat.
In this prior art planing type boat, however, water is gradually replaced by air starting from the foremost end portion of the water ballast chamber a and this, coupled with driving of an outboard motor d, causes a bow f of the boat to be lifted excessively as shown in FIG. 2 at the start of planing. Such excessive lifting of the bow adversely affects the stability of the boat in the initial stage of planing resulting in prolongation of time required for entering a smooth planing state.